An open source kiln as part fo the RepRap project?

Hi all

I've been experimenting with lost PLA casting 3D printed parts, however like most people I don't own a kiln. Looking around the options are very limited, I can't justify $1000 on a desktop kiln or move to a place with a large outdoor space. I'm wondering about how feasable it would be to start a project for an open source desktop kiln suitable for small makerspaces, individual makers and for potters. Would something like this fit on the RepRap wiki? The kiln could produce its own refractory bricks and would be helpful for creating metal parts using lost PLA casting and also potentially bonded metal powder. I think it could be of interest to quite a few people for several reasons:

Motivation

• High cost of commercial alternatives despite apparent low cost of materials
• Multiple use cases from multiple user groups (pottery, lost PLA casting, 3D printed ceramics, jewellery)
  The multiple user groups are all experienced makers in one way or another
• Existing low cost alternatives are all large scale and require outside space where you can make a big mess, which isn't available to a lot of people
• People are already working on parts of the problem (e.g there's already a semi open (CC BY-NC) source kiln controller and people are sharing designs but not collaborating)

Existing resources

• Low technical skill required to participate in designing the kiln body
• Some existing open source software and hardware could be used, e.g 3D printing software and control hardware which could bring a lot of functions e.g programmable temperature cycles, logs, safety feature etc).
• Large and passionate existing online communities, e.g r/ceramics has 7500 subscribers, large Facebook groups
• The project can be broken down into components, partial success is still useful, e.g kilns can be used at different temperatures for different materials, commercial kiln controllers are available but still very expensive.

Materials

• Relatively low cost materials meaning its easy to start developing
• Accessible materials, most available in a hardware store except the insulation, temperature sensor and control board, all available off Amazon at low cost
• Minimal tools required to build
• Relatively simple mechanics compared to something like 3D printing.

What do people think? How could I start something like this on the RepRap wiki? Does it fit? My only other idea of a place it could go is Open Source Ecology, but their forums don't seem to work any more which is a shame,

Thanks

What temperature are you aiming for?

There are multiple temperatures which could be useful

700C will let you melt aluminium, so you can do lost PLA casting
1400C will let you fire porcelain, useful for firing printed clay
1500Cish you can melt glass

There are commercially available desktop kilns that reach these temperatures but they expensive

Make your own for very little. [www.youtube.com]

I've also wanted to look at lost PLA casting. I've done lost wax castings before, which are of course much simpler on a small scale.

I would be interested in such a project on an affordable scale, for taking small 3d printed parts to metal in aluminum or bronze.

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

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cwaa
Make your own for very little. [www.youtube.com]

Thanks but this is not really suitable for what I'm looking for, I want to create an open source electric kiln which can be used in non dirty environments

Take the design of the above kiln and replace the propane (did not watch the video fully) heat source with nichrome wire. That's about as "clean" as melting metals gets.
[www.youtube.com]
This guy used a welder and some fire bricks for the kiln body, but there is nothing stopping you from using the bucket and concrete idea from the other video and the nichrome wire from this video. Nichrome wire is also probably the cheapest and most readily available electric heating element you'll find that can get to the temperatures you need.

Finally, a kiln is not a "desktop" item. Take that thing outside, away from flammable objects and where you have good ventilation. I have never seen anyone (even youtube amateurs) do aluminium castings on their desktop. The closest thing I've seen is in a garage which is perfectly sensible (concrete floors, good ventilation).

If you have ever worked around molten metal, you will decide very quickly that you want the kiln outside or in a fireproof environment with a lot of air flow. Are you aware that even a teaspoon of moisture in the metal you are melting can result in a very destructive explosion. Yea, you need that on your desktop. What happens when you have a spill?

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John Cummings
Hi all

...
What do people think? How could I start something like this on the RepRap wiki? Does it fit? My only other idea of a place it could go is Open Source Ecology, but their forums don't seem to work any more which is a shame,

Thanks

I suppose you have already experimented using, making mold, casting metal and want to share your experience. How about starting by showing a prototype or a drawing with specs of what you did and intend to do ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Hi! I've been working on an open source electric kiln:

RepKiln Hackaday Project Page

I plan to put the information on the RepRap wiki after I've finished it. Not that there can only be one kiln project on the wiki, of course... So, John Cummings, I say feel free to add a kiln project to the wiki!!

As far as how to start, I started my project by making a simple heat transfer model to get an idea of size and power requirements for the desired temperatures. At the same time, I started looking at what to use for bricks and options for how to assemble the kiln from a structural standpoint. All these decisions are logged in the build logs on the hackaday project. There are some heat transfer models and OpenSCAD designs at this git repo too:

RepKiln Git Repo

-Matt

Thanks very much all, I've made a start on an outline here [reprap.org] please do add to it

Edited 1 time(s). Last edit at 09/22/2018 06:42PM by John Cummings.

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John Cummings
Thanks very much all, I've made a start on an outline here [reprap.org] please do add to it

How about a picture of your kiln ? How you made it, use etc ;;; ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Hi John, thanks for starting the page! I added a few additional links. The little Rapidfire kiln looks interesting. To be honest, I'm not sure an open source alternative would cost much less than the list price of $565 for the Rapidfire.

If you have an idea of the size and available power you are thinking of, you could try using some of the python script heat transfer models on the Repkiln github repo. You can plug numbers into the script called kiln_heatup.py to get an estimate for different sizes of kilns.

For a desktop/benchtop kiln, for safety, it is probably quite important for the thing to be in a metal box (better yet take it outside as Trakyan suggests). Finding or designing a suitable low-cost, easily-fabricated metal box might be the first place to start with the structural design. Alternatively, people make very small kilns to go in a microwave oven - maybe one of these could be modified with an electric heater. Microwave kilns are pretty cheap on amazon and ebay, but perhaps they are too small for what you are thinking.

Regarding the controller, it would probably be pretty easy to modify a standard 3D printer controller and software to run a kiln. One option is to make a special interface board with a high temperature thermocouple reader chip and a hefty relay for switching on/off the heater, and then just connect this to a standard controller like Gen 7, etc.

I have used induction heaters in the past and I think a great way to heat something quickly is with induction heating.

[www.ebay.com]

The link is for a really cheap component that could be used as part of a heater or a toy heater.

There are complete units that are also available. They could be used to generate heat for burn out, or melt metals, including stainless steel if you size everything correctly.

[www.ebay.com]

[www.ebay.com]

I am not attaching the links to entice you to buy, but to show another way. It is quick and clean, and can be turned off and on quickly.

The idea of designing a working induction heater/ casting system that could handle the requirements of lost filament casting is a little like early 3D printing, you would not be an expert, if you built something to try, there would be risk, You may make a mistake, if it all came together and you generated a metal object that you could hold, it would be cool.

Ken

Induction heaters can't be used to burn out molds etc. They can only heat conductive materials, and even then they tend to only be very effective with steels and iron, stuff like aluminium (which is what most hobbyists seem interested in due to a lower melt Temp) doesn't interact with the induction heater coil as much and therefore doesn't heat up as much.

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Trakyan
Induction heaters can't be used to burn out molds etc. They can only heat conductive materials, and even then they tend to only be very effective with steels and iron, stuff like aluminium (which is what most hobbyists seem interested in due to a lower melt Temp) doesn't interact with the induction heater coil as much and therefore doesn't heat up as much.

You are wrong, it is usable to melt Al and other stuff ! Just needs to use a graphite crucible.
Some time ago I bought the induction heater referenced by kengineer. To use it properly, it needs proper cooling though ( pump water through the coil and a fan) plus a good power supply.
Too bad but to heat treat small steel parts, it is limited as the T° reached is barely enough for some (Curie's fault). So I heat treat my hobgear with a torch. Only a shark has better teeth
Now, to get a very good one costs a lot more.
BTW no news from the OP and his kiln.

Edited 2 time(s). Last edit at 10/17/2018 01:50AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Fair point then, I haven't used the commercial offerings but from what I've seen and done Aluminium is harder to heat. Also why induction stovetops don't work so well or at all with plain Aluminium pans or pots. I'm sure you can use a more powerful induction heater, but that all adds cost, complexity and makes it a bit more dangerous. I still reckon a regular heater is the best bet. Works equally well with all materials, cheap and not EMI to worry about.

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Trakyan
Fair point then, I haven't used the commercial offerings but from what I've seen and done Aluminium is harder to heat. Also why induction stovetops don't work so well or at all with plain Aluminium pans or pots. I'm sure you can use a more powerful induction heater, but that all adds cost, complexity and makes it a bit more dangerous. I still reckon a regular heater is the best bet. Works equally well with all materials, cheap and not EMI to worry about.

It is the graphite crucible that heats up the Al or other non ferrous material.
As for the "danger", not more, in fact even less than a resistive wire connected to the main or the use of propane.
The real danger is when inexperienced people start to play with these.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

MKSA,

Thanks for chiming in about what is possible. Induction heating can be dangerous, like printing, or working with electronics or machines.

Anyone interested in learning more about induction heating may enjoy this link: [en.wikipedia.org]

One reason I seldom post is that, those who do not know what they are talking about or understand the topic, feel as though they should post. Example: "I really don't know anything about (fill in the blank_____) but it is not good".

Induction heaters are still not great to burn out molds.

Unless you're going to use iron (or graphite) plates as a part of the mold for the induction heater to heat it up. Since most of the instructions that I've seen say to make the mold from plaster and sand, the induction heater isn't going to do anything to that at all, and certainly not the the plastic.

Fortunately we don't need to get to metal melting temperatures to burn out the molds, so we might still be able to do that with something a little less extreme, but we still (probably) want to reach vaporisation temperatures for the plastic in order to make sure that the inside of the mold is clean. Hmmm. Hard to find ignition temperature data, sees like it's a little bit variable, if I'm reading it right, it seems to be 380-407 deg C. This is still quite a bit less than the melting point of aluminum (660 deg C) but still a non-trivial temperature to heat to, and beyond the capability of most household heaters.

I suppose that you could put the mold in another graphite crucibel, but you might a rather large one.

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

[www.youtube.com]

If they can do it, it isn't that difficult isn't ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)